Bifluid boiler control



Nov. 22, 1932. H. H. Dow 1,888,311

BIFLUID BOILER CONTROL Filed' Dec. 29, 1928 ATToRN Patented Nov. 2 2, 1932 UNITED STATES PATENT oer-Ice HERBERT H. DOW, 0F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN BIFLUID BOIIER CONTROL Application tiled December 29, 1928. Serial No. 329,177.

The present invention relates to methods of control of boilers in which two separate and distinct iiuids are heated in separate circulatory s stems.

The pro lem towhich my invention is directed is connected with restriction of waste of the fluids by emergency blowing of safety relief devices, such as safety-valves. Such emergencies arise through failure of control of heat input, e. g., supply of fuel to the furnace or sudden cessation of use of the heat in connected heat consuming systems, such as power cycles and the like.

My invention provides, brieiy, that the eX- cess heat entering one of the two circulatory systems shall be transferred by the fluid therein to the fluid in the other circulatory system through a stabilizing boiler feed heater, thereby disposing of said excess heat and avoiding undesired pressure rise in the one circulatory system so relieved, meanwhile permitting the safety-valve on the other circulatory system to blow, if it must, either to waste or to a vapor conserving condenser. The blowing to waste or to a conservation condenser is thereby restricted to one uid only.

To theacco'mplishment of the foregoing and related ends, the invention, then, consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In the single Adrawing accompanying this application I have shown in somewhat diagrammatic form a bi-fluid boiler and connected heat utilizing and fluid handling steps disclosing in a general way bi-fluid boilers and connected heat consuming load. For the purpose of simplification, a diphenyloxide-water boiler system is illustrated and described.

A boiler furnace is indicated by the broken line l enclosing the water tubes 2, the diphenyl oxide tubes 3 and drums A: and 5.

Drum 5 is connected by pipe 6 to drum 7 through which the water tubes 2 are led and from which they emerge at 8. A return circulation pipe 9 connects drum 7 with drum 4 and provides for return of the Huid from 7 to 4 whence it rises through tubes 3 to drum 5 and to 7 via 6. There is indicated at l0 a vapor heat utilizing step, for example, a power cycle to which the steam is supplied by pipe 11 and to which also diphenyl oxide (D. l. O.) is supplied by pipe 12 for such uses as prime mover jacket heating, steam reheatinfr, power generation, etc.,

From the power cycle l() the water condensate is drawn by pipe 13 into the condensate collection and return steps indicated at 14 from which the condensate is returned to the boiler via pipe 15 through an indirect stabilizing feed-water heater 16.

F rom the power cycle 10 the diphenyl oxide condensate is led by pipe 17 to the condensate collection and return steps indicated at 19 from whence it is returned to the boiler via the pipe 20. A back-pressure valve 2l of the piston or balanced type is connected with the diphenyl oxide vapor main 12 and the discharge therefrom is piped via 24 to the indirect stabilizing feed-Water heater 16, in which the diphenyl oxide vapor passed by valve 21 is brought into heat transfer relation with the feed water and its heat used to heat the latter. A safety-valve for the steam system is provided at 22 and one for the diphenyl oxide system at 23. The latter is set to blow only in extreme emergencies and it is not intended it shall operate otherwise, it being the otiice of the relief-valve 2l to operate irst to relieve excess pressure in the diphenyl Oxide system. The steam'relief-valve 22 may be connected, if desired, to a condenser adapted to condense the steam or it may be connected to any other consuming unit or step.

It will be seen that should the heat input to the boiler rise in excess of the heat requirements of the power cycle connected therewith, the pressure in the two circulate Systems will rise and unless the heat input e reduced through the action of other controls, or should such controls fail to function, the vapor pressures in the circulatory systems must be relieved. The function of reliefvalve 21 will be to by-pass the excess vapor of the diplienyl oxide around the power cycle into the stabilizing feed-water heater 16 wherein its heat content will be transferred to the water system still further increasing heat therein. The safety-valve 22 will then be relied upon to relieve the excess pressure in the steam system.

Should the consumption of heat in the power cycle be suddenly discontinued for any cause and suitable heat input changes not be effected in the boiler or not be capable of bein effected with sufficient promptiiess (as might be the case with sudden loss of load in a connected power cycle) rise in pressure in the circulatory systems would occur, consequent upon the heat stored in the boiler setting or the continued supply of heat at a high rate thereto, in which case valves 21 and 22 would function as already herein described, and in extreme emergency, valve 23 would open.

It will be seen that with the arrangement provided by my invention, no valuable diphenyl oxide or other high boiliig point fluid will be blown to waste either in vapoi' or liquid form, except under extreme emergency, and only the vapor of the low boiling point fluid which will usually be water will escape from the system through a safety outlet. This desirable action will be brought about through the use of relief-valve 21 set at a proper relief pressure combined withthe use of the stabilizing feed-water heater 16, by means of which the excess heat content of the high boilin fluid system will be passed out through va ve 21 and be transferred to the water circulatory system in 16. In this way, excess heat content in the system causing ressures in excess of those at which it is esired to operate will be relieved from one fluid system only, namely, the low boiling fluid system which, as above stated, being usually a water system entails no loss of high priced or valuable fluid.

My invention is applicable not only to systems using water and diphenyl oxide, but to systems using an two fluids of different boilin points. Suc low boiling fluids as alcoho and/or volatile hydrocarbons may be substituted for the water and such high boiling fluids as diphenyl, and the like, may be substituted for the diphenyl oxide.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following Vclaims or their equivalent be employed.

I therefore particularly point out and distinctly claim as m invention 1. A method o the character described which comprises simultaneously supplying vaporizing heat to a low and a high boiling point'liquid by passing them through separate containers in heat absorbing relation with a common source of heat,'bringing thtl so heated fluid products into temperature balancing heat transfer relation, utilizing the so treated vapor of the low boiling point liquid while utilizing the vapor of the high boiling point liquid, and preventing excess pressure development in the high boiling point liquid vaporizing and utilizing system by transferring to the low boiling point liquid boiler feed at least part of the heat that would otherwise cause said excess pressure.

2. A method of the character described, which comprises supplying vaporizing heat to a low and to a high boiling point liquid while passing them through se arate vaporizers, bringing the so heated fluid products of said high and low boiling point liquids into temperature balancing heat transfer relation, then passing the so treated vapor of the low boiling point liquid through a power cycle while passing the vapor of the high boiling point liquid through a heat utilizing step, and preventing excess pressure development in the high boiling point liquid vaporizing and utilizing system, by transferring to the low boiling point liquid boiler feed at least part of the heat in the vaporized high boiling point liquid that would otherwise cause said excess pressure.

3. In a method of controlling and stabilizing a bi-fluid boiler in which two liquids having different boiling points are heated and vaporized in separate circulatory systems and brought into temperature balancing heat transfer relation with each other before use of either in a heat utilizing step, the steps of passing the vapor of the low boiling point liquid through a heat utilizing cycle, simultaneously passing the vapor of the high boiling point liquid through a heat utilizing cycle, and avoiding excess pressure development in the high boiling point liquid vaporizing and utilizing system and loss of high boiling point liquid by transferring from the fluid products of said high boiling point liquid to the boiler feed of the low boiling point liquid the heat that would otherwise cause said excess pressure.

4. ln a bi-fluid boiler system, the combination of separate varporizers for a high and a low boiling point liquid, means for ininiediately bringing the fluid products from each of said vaporizers into indirect teinperature balancing heat transfer relation, means for utilizing heat carried by the vapors of said high and low boiling point liquids, a boiler feed heater in the boiler feed line of the lower boiling point liquid adapted to bring said boiler feed into heat absorbing relation with fluid products from the high -boiling point liquid system, and pressure controlling means for limiting the maximum pressure on the high boiling point liquid system by by-passing to said boiler feed l heater any excess vapor generated from said high boiling point liquid.

5. In apparatus of the character described, the combination of a one-pass tubular steam generator, a drum to contain a body of a heatstoring fluid, a conduit therethrough for the generated steam in indirect contact with a liquid portion of said fluid, common means to supply heat to said generator and to said v body of heat-storing fluid, a conduit to carry vapors from said drum, a vent valve therein to liberate vapor therefrom ata predetermined pressure below the safety blow-oft pressure, a feed-water preheater, means to bring vapors liberated by said vent valve in to heat exchange relation with the water in said preheater, and means to return the cooled and condensed vapors to said drum.

6. The method wherein steam is generated from water under pressure in tubes, in onepass through a heating zone, which comprises the steps of subjecting such Water in a portion of said pass to a sourceof heat-to produce a mixture of steam and water wherein the steam predominates and the water is present in amount in excess of that present in steam delivered from a conventional drum type boiler under normal ,operating conditions, whereby the one-pass tubes exposed to the source of heat are protectedfrom injuryI by over-heating because o Water in liquid form being present throughout the-length thereof, subjecting such mixed Huid immediately to a temperature-balancing heat exchange with a body of a heat-storing uid having a higher boiling point in liquid state than water under thev same pressure, said higher boiling point liquid being heated normally under pressure of the saturated vapor thereof to a temperature approximating, but above, the desired working temperature for the steam, whereby the evaporation of the Water is completed and variations in temperature incident to uctuating steam demand are reduced, preventing a rise in temperature and pressure of such high boiling point Vagent above a predetermined maximum, well below the safety bloW-oif preure, by venting at least a portion of the vapors thereof when the temperature and corresponding pressure exceed such maximum, passing such vented vapors in vheat exchange relation with the feed-Water on its way to the L one-pass vapor generator, and returning the thereby condensed high boiling point liquid to the main body thereof for recycling.

Signed by me this 24th day of December,

HERBERT H. DOW. 

